GCN Circular 45904
GRB 261011A: Optical follow-up observations with Kinder
From: Janet Chen at National Central University
Issued: 2026-10-11 16:42 UTC
Type: GRB, Optical Transient
A. Aryan, Z.-Y. Chen, T.-W. Chen, W.-J. Hou, Y.-H. Lee (all NCU), A. K. H. Kong (NTHU), S. Yang (HNAS), S. J. Smartt, J. H. Gillanders (both Oxford), A. Sankar.K, K. N.-T. Ho, A. Dutta, M.-H. Lee, C.-S. Lin, Y.-C. Pan, C.-C. Ngeow, C.-H. Lai, H.-C. Lin, H.-Y. Hsiao, J.-K. Guo (all NCU), Z. N. Wang, D. C. Qiang, L. L. Fan (all HNAS), Y. J. Yang (NYUAD), H.-W. Lin (UMich), K. W. Smith, H. F. Stevance, S. Srivastav, L. Rhodes (all Oxford), M. Nicholl, M. Fulton, C. Angus, A. Aamer (all QUB), T. Moore (STScI), A. Schultz and M. Huber (both IfA, Hawaii) report:
As part of the Kinder collaboration (Chen et al. 2025, ApJ, 983, 86,doi:10.3847/1538-4357/adb428), we conducted multi-band optical follow-up observations of GRB 261011A, detected by SVOM (Huang et al., GCN 45895) and Swift (Cenko et al., GCN 45896).
Imaging was acquired in the g-band using the 1m Lulin One-meter Telescope (LOT), and in the r- and i-bands using the 40cm Seisi Lulin Telescope (SLT). Our observations started at MJD 61324.6155, approximately 0.99 hr after the Swift/BAT trigger.
The optical counterpart reported by Swift/UVOT (Cenko et al., GCN 45896), GOTO (O'Neill et al., GCN 45897), and more instruments (Fu et al., GCN 45898; Izzo et al., GCN 45899; Wu et al., GCN 45900; Yin et al., GCN 45901; Shi et al., GCN 45902) was clearly detected in all three bands.
We used AutoPhOT (Brennan & Fraser 2022, A&A, 667, A62) to perform PSF photometry. Preliminary measurements are as follows:
Telescope | Filter | MJD (start) | t-t0 (hr) | Exposure (s) | Magnitude
LOT | g | 61324.6155 | 0.99 | 60 * 1 | 20.47 +/- 0.10
SLT | r | 61324.6157 | 1.04 | 300 * 1 | 19.91 +/- 0.07
SLT | i | 61324.6194 | 1.09 | 300 * 1 | 19.69 +/- 0.07
Using the nearly simultaneous g- and r-band measurements at approximately 1.04 hr after the trigger, and correcting for Galactic foreground extinction, we obtain (g-r) = 0.64 +/- 0.11 mag. Using the earliest r- and i-band measurements, we obtain (r-i) = 0.20 +/- 0.10 mag. Thus, the source shows a relatively red (g-r) colour while remaining considerably flatter between r and i.
The presented magnitudes are calibrated using field stars from the ATLAS-RefCat2 catalog from MAST (Tonry et al. 2018, ApJ, 867, 105) and are not corrected for Galactic foreground extinction of A_g = 0.07, A_r = 0.05 and A_i = 0.04 mag in the direction of the transient (Schlafly & Finkbeiner 2011).
The methodology, details on the Lulin Observatory telescopes, and a compilation of our optical follow-up campaign for FXTs discovered within the first year of operation of the Einstein Probe mission are presented in Aryan et al. 2025, ApJS, 281, 20, doi:10.3847/1538-4365/adfc69.
Every one of the gamma-ray bursts GCN reports is posted here.
Relayed automatically from NASA's General Coordinates Network.
Transient Alerts » in reply to GRB 261011A — GRB, X-ray Transient
In plain words Notable
On 11 October 2026 two satellites, SVOM and Swift, caught a long gamma-ray burst (a brief flash of high-energy light from a distant exploding star) in the southern sky. It lasted roughly a minute or more, depending on the instrument. Within minutes, telescopes around the world saw a fading visible-light and X-ray afterglow at the same spot. Two large telescopes measured the distance from the light's fingerprints: the burst happened at redshift 2.407, meaning the light left roughly 11 billion years ago. The afterglow faded below detection within about a day, and no host galaxy has been clearly detected. It is most likely an ordinary long burst from the collapse of a massive star. Swift's first report of an unusual light curve was withdrawn after a closer look showed that part of it came from noisy detectors.
How unusual is it? Most gamma-ray bursts have no measured distance, but this one has a confirmed redshift (2.407) from two independent telescopes plus a bright afterglow seen in many wavelengths; otherwise its properties look typical, and the initially reported oddity turned out to be instrumental noise.
Written by an AI model (claude-sonnet-5-5) from the official reports in this thread, and rewritten as new reports arrived (version 9); last updated . It may contain mistakes: the reports themselves are the authority.
GRB 261011A: Optical follow-up observations with Kinder
The whole thread (32 posts)
- GRB 261011A — GRB, X-ray Transient
- GRB 261011A: 1.3m DFOT optical upper limit
- GRB 261011A: SAO RAS and AbAO optical observations
- GRB 261011A: Later-epoch J-band upper limit from the SYSU 80 cm infrared telescope
- GRB 261011A: GECAM-B observation
- GRB 261011A: Swift-XRT refined Analysis
- GRB 261011A: Enhanced Swift-XRT position
- GRB 261011A: 10.4m GTC spectroscopic redshift (z = 2.407)
- GRB 261011A: Swift-BAT refined analysis
- GRB 261011A: REM optical/NIR observations
- Konus-Wind detection of GRB 261011A
- Updated explainer: what the latest reports add (AI-written)
- GRB 261011A: SOAR optical afterglow observations at ~17 hours
- GRB 261011A: VLT/X-shooter redshift constraints
- GRB 261011A : MITSuME Akeno optical afterglow candidate detection
- GRB 261011A: Optical followup from Sichuan South Observatory
- GRB 261011A: GMG Optical Observation
- GRB 261011A: Liverpool Telescope optical observations
- GRB 261011A: J-band observations by the SYSU 80cm infrared telescope
- GRB 261011A: continued LCO optical observations
- GRB 261011A: GROWTH-India Telescope optical observations
- GRB 261011A: Optical upper limits with a 28cm telescope in Chengde
- Swift GRB 261011A: Global MASTER-Net observations report
- GRB 261011A: Optical follow-up observations with Kinder
- GRB 261011A: SVOM/C-GFT optical observations
- GRB 261011A: LCO optical observations
- GRB 261011A: SVOM/VT optical observation from VHF data
- GRB 261011A: LCO optical observations
- GRB 261011A: TRT optical afterglow detection
- Explainer: what this is and why it matters (AI-written)
- GRB 261011A: GOTO optical counterpart detection
- GRB 261011A: Swift detection of an unusual burst